Grid structure for vacuum tubes and the like



March 26,1946. F; J1 BICBIGLEYJ j. 2,397,233

GRID STRUCTURE FOR VACUUM TuB sL- jun THE LIKE I 1 INVENTOR.

J FM ([51:79 j v Patented Mar. 26, 1946 Frank J. Bingley, Philadelphia, Pa., assignor to Philco Radio and Television Corporation, Philadelphla, Pa., a corporation of Delaware Application December 14, 1943, Serial No. 514,256

6 Claims.

The present invention relates to vacuum tube structures and more particularly to a vacuum tube grid of the type having parallel grid wires.

In constructing such vacuum tube grid structures, the common practice in the past has been to use a generally rectangular or square frame having a suitable opening therein as the support for parallel arranged grid wires. To form the grid wires it has been found convenient to wind the grid wires completely around the grid frame supporting structure so that on one side of the grid frame the wires are arranged parallel to each other and substantially perpendicular to opposite edges of the frame. Those wires are then bonded to the frame adjacent the edges of the frame by any suitable securing process, such as brazing. After the wires have been brazed in position, the remaining wires on the other side of the grid frame are removed. It has been found that grid structures formed in this manner have the disadvantage of being subject to warping by heat. The grid wires when subjected to heat expand at a greater rate than the grid supporting frame so that not infrequently the expanded heated grid wires sag or are otherwise displaced from the plane in which the grid wires originally were positioned and secured.

By the present invention there is provided. a parallel-wire grid structure which may be subjected to heat without incurring the disadvantage of having the grid wires displaced out of their original plane. In accordance with the present invention, this is accomplished by securing the wires in position on a frame in a manner to subject them to initial deformity adjacent the points where the wires are secured, so that when the wires are heated they are prevented from becomingfdisplaced from their original plane, because the initial deformity of the wires causes any displacement thereof to occur in the plane of the wires which are caused to remain parallel.

It is therefore an object of the present invention to provide a new method of constructing a grid structure of the type described.

It is another object of the present invention to provide an improved method of constructing a parallel-wire grid structure wherein the grid Other and further objects will become apparent connection with the accompanying drawing wherein:

Fig. 1 illustrates in perspective a partially completed grid structure formed in accordance with the method of the present invention;

Fig. 2 illustrates in perspective a completed grid structure formed in accordance with the present invention; and

Fig. 3 shows one of the grid wires enlarged and illustrates the action which takes place upon heating thereof.

Referring to the drawing it will be seen that a grid frame which is generally rectangular or square in outline has been formed in accordance with the present invention in two similar sections H and i2, each having one-half of a centrally arranged aperture l3 and 14, respectively, which may comprise a semi-circle. In accordance with the method of the present invention the two halves, II and I2, of the grid frame are initially displaced laterally with respect to each other in a common plane by a predetermined amount, and are also slightly separated, as shown in Fig. 1. The two displaced grid frame portions H and I2 may be secured in a suitable J'ig as is customary practice in manufacturing production methods. With the two halves of the grid frame H and 12 thus arranged, a suitable fine resilient wire is then completely wound around the grid frame members so as to provide across one face thereof spaced wire strands l5 which are parallel to each other and substantially perpendicular to opposite edges of the grid frame. Each of the said strands is then secured to the face of the grid frame by a suitable bonding process, such as brazing, as indicated at the areas 16 and I]. After the wire strands 15 have been secured in position by spot welding or brazing or in other suitable manner, the other portions of the wound wire are cut off, leaving the parallel wires l5 as shown in Fig. 1. When this operation has been completed, the two frame sections II and [2 are removed from the jig or other holding means and are then moved so as to align the displaced centers thereof and to bring their edges into abutment, as shown in Fig. 2, and the edges l8 and IS on each side of the aperture 20 are then secured in position by bonding or spot welding indicated by the stippled area 2|. When the two grid frame sections H and i2 are aligned in positions as shown in Fig. 2, each of the wires I5 is initially deformed or bent at points adjacent the bonded portions 16 and IT.

The initial positioning of the frame sections, as shown in Fig. 1, should be such that the grid wires will at least be taut when the frame sections v r of the wires appended claimsl v e are brought intoalignment as in Fig. 2. If desired, the initial positioning of the frame sections may be such that grid wires will be placed under slight tension when the frame sections are positioned as in Fig. 2. In such case, the tension will reduce their tendency to elongate. v f? KI i .By reason of the structure'abov mentioned,- the grid wires are prevented from being displaced from their original plane, when they are heated during-operation of a tube embodyingthe structure. The action which takes placedur'ingfheat ing and expansion of the wires may be clearly seen by considering the actlon 'gf ;-one -wireas The solid line representation,

shown in Fig. 3.

- for a vacuum tube, utilizing a two-section grid supporting frame, which comprises initially displacing said sections a predetermined amount, arranging on said displaced sections a plurality of shows the normal position of a wire l'5*whose end wiresto said frame adjacent said edges, removing portions 22 and 23 are securedas above'described;

It will be seenthat the wire has revers e bends adjacent the secured end portions. the resilience of the wire and the-stressesproduced by the deforming or bending thereof, any elongation nf-the wire due to heating'will-cause thewire'to; assume a positionsuch as shown by the broken line; The -deformed portions ofthe wire act as resilient cantilevers and tend to -move counter-clockwise, as .-viewed in the; figure. Any elongation of the wire will permit-these cantilever portions to move and thuscompensate for Owing to 3. The method of constructing a grid structure for a vacuum tube, which comprises forminga rectangular grid supporting frame in twosections, f jldi'splacing 'said'sections with respect to each other, winding a wire about said displaced sec-V ,tionsi to arrangeicn one face thereof spaced parallel:wiresTsubstantially perpendicular to opposite edge's'of said frame, bonding said parallel the wires on the'opposite side of said frame. aligning said frame sections, and securing said sections in aligned positiom 7L 1 4. The method amendments agridlstructure for avacuum tube, utilizing a. ltwo-sectionlgr'id supporting frame, .whlcnfcomprises. dis'placing suclr'elongation. Thus all of the gridjwires will assume similar new positions and lwill -remain substantially parallel in their common plane.

It will be noted that the eifective portion of each gridwire within the area of the aperture 20 will remain substantially straight.

1 Thus the structure provided by the invention frame structure has been shown as being of square shape and as havinga circular opening, it

is of course to be understood thatother suitable configurations may beutili'zed and that such modifications are to be deemedi'within the scope and spirit of. the invention as set forth in the I'claim: 1

. l.v A method of forming a parallel-wire' grid structure for a vacuum tube or the like,'which comprises arranging the grid wires rectilinearly inparallel relation, securing the end portionsof .the wires and then relatively shifting the opposite secured end portions ofthe wires in their plane.

said sections with respect tcfeach' vother in .the plane of saidsections, arranging-onsaid displaced sectidns a plurality of parallel wires, securing said 7 Wires to said sections, aligning" said sections to deform the wires adjacent their points offsecure' merit, and securing.said-sectionsfinalignedrelation',

5. The method. of constructing a grid structure for a vacuum tube, which comprises, forming-a flat apertured rectangular grid supporting frame in two similar sections, displacing said. "sections infa commonplane a predetermined amount with z V on'ftheopp'osite side of said frame, aligning said frame, sectio'ns'to deform said. wires adj a'cent .the

' pointswhere they are secured to said frame, and

bonding. the edges of said alignedse'ctions to secure said sections in permanent ,position.1j,

6. A gridstructure for avacuum tubeIor the like, comprising a frame, and' a plurality of substantially parallel coplanarfspaced resilient wires extending across-saidlfra'me and haying' their end portions secured to the frame, the points 'of secu'r'ement of the. endsofeachwire beingrelatively offset, andthe end portions of leach, wire being ccnsequentlyldeformed so asto, causefsaid portions to act as resilientjcantilevers in theicommon plane of the wires .whenever the wires. be:- come elongated, whereby the wires are caused toremaln, substantially parallel'intheir, common 

